Electronic shifting systems and methods

ABSTRACT

The invention provides a wireless control system for a bicycle, including at least one shift unit including a shift actuator, and a master control unit in communication with the shift actuator. The master control unit transmits on a channel and listens for noise on the channel. When the master control unit receives an input signal from the shift actuator, the master control unit transmits a plurality of shift signals corresponding to the input signal for a message duration time if the channel is free of noise.

REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.14/534,363, filed Nov. 6, 2014, which is a divisional of U.S. patentapplication Ser. No. 13/712,616, filed Dec. 12, 2012, now U.S. Pat. No.8,909,424, claiming the benefit of U.S. Provisional Patent ApplicationNo. 61/712,636, filed Oct. 11, 2012.

BACKGROUND OF THE INVENTION

The invention relates to bicycle gear changing systems. In particular,the invention is directed to systems including wirelessly actuatedbicycle gear changers. The systems include bicycle gear changerscontrolled by a wireless control signal, wherein the wireless controlsignal is generated by a bicycle control component.

One prior art electromechanical shifting system required a wirelesstransmitter and receiver to be on continuously. To conserve energy, avery low-power & low-range transceiver was utilized. However, thelow-power transceiver suffered from poor wireless performance. A morerecent system requires a periodic beacon signal which will also alwaysconsume battery power.

There is a need for a highly reliable and more secure wireless controlsystems for bicycles. The invention satisfies the need.

SUMMARY OF THE INVENTION

The invention uses a relatively higher-power transmitter and receiver,but power is conserved by turning the transmitter and receiver off whennot in use and by power cycling the transmitter and receiver when thebicycle is active. The inventive systems may be made more secure byrequiring physical access/interaction to pair the shifters (i.e., thecontrol componentry) with the gear changers.

One aspect of the invention provides a wireless control system for abicycle, including at least one shift unit including a shift actuatorand a master control unit in communication with the shift actuator. Themaster control unit transmits on a channel and listens for noise on thechannel and after receiving an input signal from the shift actuator andtransmits a plurality of shift signals corresponding to the input signalfor a message duration time if the channel is free of noise.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a side view of a drop-bar style bicycle with wirelesscomponents installed thereon.

FIG. 2 is a view of a shifter/brake assembly with an integrated mastercontrol unit (MCU).

FIG. 3 is a flat type bar with shift units wired to a discrete controlunit.

FIG. 4 is a rear gear changer according to an embodiment of the presentinvention.

FIG. 5 is a front gear changer according to an embodiment of the presentinvention.

FIGS. 6-9 are schematic views of a wireless communication/controlsystem.

FIG. 10 is a wake/sleep timeline of a gear changer control unit (SCU).

FIG. 11 is a timeline of the SCU transmitter and receiver and the MCUtransmitter and receivers.

FIG. 12 is a wake/sleep/TX timeline of the MCUs.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the invention will herein be described with reference tothe drawings. It will be understood that the drawings and descriptionsset out herein are provided for illustration only and do not limit theinvention as defined by the claims appended hereto and any and all theirequivalents. For example, the terms “first” and “second,” “front” and“rear,” or “left” and “right” are used for the sake of clarity and notas terms of limitation. Moreover, the terms refer to bicycle mechanismsconventionally mounted to a bicycle and with the bicycle oriented andused in a standard fashion unless otherwise indicated.

Referring to FIG. 1, a bicycle 20 with a drop-bar type handlebar isshown with a wireless communication/control system 22 in accordance withone embodiment of the invention. The wireless control system 22 includesat least one shift unit 24 (shifter) which may be mounted to a bicyclehandlebar 26 attached to the bicycle. The bicycle 20 wireless controlsystem 22 also may have one or both of an electromechanical front gearchanger 28 and an electromechanical rear gear changer 30 mounted to thebicycle frame 32 part of the bicycle 20. The gear changers 28, 30 may bederailleurs or internal gear hubs, for example. The control system 22may be usable with other systems and/or components of the bicycle 20,such as suspension components and systems, controllable seat posts,power meters, cadence meters, lighting, bicycle computers, and so on, inaddition to gear changers or in the alternative to gear changers. Forcontext, the bicycle 20 will typically have a drive assembly 33, withone or more front chainrings 35 connected to a plurality of rearsprockets 37 by a chain 39 as is known in the art.

FIG. 2 shows a drop bar shift unit 24 in greater detail. The shift unit24 may include a brake support bracket 34 mountable to a handlebar, abrake lever 36, a shift lever 38, (which is one form of a shiftactuator, e.g., a button or the like), operatively coupled to a shiftswitch 40, a front gear changer shift toggle button 42, and a mastercontrol unit 44, and a power source such as a battery 46. Shift switch40 may be actuated by any suitable actuator/device, such as a momentarycontact button, for example.

Referring also to the embodiment of FIG. 6, the master control unit 44may receive input signals from the shift switch 40 and front gearchanger (FD) shift toggle button 42, and also includes a CPU 48 providedin communication with the shift switch for processing the input signals,a memory component 50 in communication with the CPU, an optionalindicator such as a LED 52 to display status signals generated by theCPU, and a wireless transmitter and receiver 54. It will be noted thatthe term “transmitter and receiver”, as used herein may include atransceiver, transmitter-receiver, or radio, and contemplates any deviceor devices, separate or combined, capable of transmitting and receivingwireless signals, including shift signals or control, command or othersignals related to some function of the component being controlled.

Shift units 24 may be supplied in pairs 24 a, 24 b and are typicallyinstalled on the handlebar 26, or a similar component, with one shiftunit located to be operated with the right hand and the other to beoperated with the left hand. When two separate shift units are employed,there may be a pair of master control units (MCU) 44 in the system 22,one in each of the two units 24 a, 24 b. Shift units 24 may bepositioned anywhere within reach of the user, and multiple units and orshift switches 40, or the like, may be positioned thereon, such as inthe type of bicycle known as a time trial bicycle which can have shiftunits on both the bars and bar extensions.

In one embodiment, for example, the CPU 48 used may be an AtmelATmega324PA microcontroller with an internal eeprom memory and thetransmitter and receiver 54 used may be an Atmel AT86RF231 2.4 GHztransceiver utilizing AES encryption and DSS spread spectrum technologysupporting 16 channels and the IEEE 802.15.4 communication protocol.Other suitable CPUs and wireless transmitter and receivers arecontemplated.

In one embodiment of the wireless control system 22, the shift lever 38on the right shift unit 24 a, when actuated, causes the generation of ashift signal corresponding to an upshift, which is actuatable by therear gear changer 30. The shift lever on the left shift unit 24 b, whenactuated, causes the generation of a shift signal corresponding to adownshift, which is actuatable by the rear gear changer 30. Upshiftcorresponds to a gear shift to a higher gear (e.g., smaller rearsprocket 37) and downshift corresponds to a gear shift to a lower gear(e.g., larger rear sprocket 37). A front shift actuator 42, which may bein the form of a button, and is an optional element, may be provided onboth shift units 24 and when operated, transmits a toggle front shiftsignal to toggle the front gear changer 28. Therefore, each MCU 44 ofeach shift unit 24 can wirelessly transmit shift signals that arereceivable and may be actuatable by each gear changer.

It may also be desirable to add a modifier actuator 56 to, for example,the shift unit 24. A modifier actuator 56, which may be in the form of abutton, does nothing when operated alone, but when operated incombination with another actuator causes the generation of a differenttype of signal (i.e., not a shift signal). For example, when the shiftlever 38 of unit 24 a is pressed in combination with the modifieractuator 56 a “shift alignment inboard” or trim command, or the like,can be issued instead of an “upshift” command. The modifier actuator 56may be located on the shift lever 38 and be in communication with theMCU 44.

FIG. 3 shows another embodiment with the system 22 adapted to a flat-barapplication. In this embodiment, right and left shift units 124 a, 124 bare provided. A shift junction box 58 may be connected by signal wires60 to the right shift unit and left shift units 124 a, 124 b. A singlemaster control unit 144 may be located in the shift junction box 58 thatreceives signals from the left and right shift units 124 a, 124 b (FIG.8). The single master control unit 144 includes components similar tothose of MCU 44 in the shift units 24. Specifically, the MCU 144includes a CPU 148 in communication with the left and right shift units124 a, 124 b, a memory component 150 in communication with the CPU, atransmitter and receiver component 154, and a LED 152 to indicateoperating conditions of the MCU 144. A battery 146 provides power to theMCU 144 and a modification actuator 156 is provided to modify theoperation of the MCU.

Although this flat-bar embodiment is shown with a shared single mastercontrol unit 144, two master control units could be employed.Alternatively, junction box 58 and shared master control unit 144 couldbe employed in the drop bar version described above. Each of the shiftunits 124 a, 124 b may have a shift switch 140, which is responsive tothe shift levers 38 of shift unit 24 described above.

An embodiment of an electromechanical rear gear changer 30 (RD) is shownin FIG. 4. In general, electromechanical gear changers are known in theart. The present rear gear changer includes a power source 62 (battery),a motor unit 64, and a gear changer control unit 66 (SCU or “slavecontrol unit”). The gear changer control unit 66 (FIG. 7) may include aCPU 68 to process signals/commands, and the like, a wake sensor 70operatively connected thereto, a memory component 72, a function button74, an indicator such as a LED 76, an output 78 to send control signalsto the motor unit 64, and a transmitter and receiver 80 for sending andreceiving wireless signals. The motor unit 64 receives and executesposition trim commands and/or gear change commands from the gear changercontrol unit 66.

An embodiment of an electromechanical front gear changer 28 (FD) isshown in FIG. 5. Like the rear gear changer described above, the frontgear changer has a power source 82 (battery), a motor unit 84, and agear changer control unit 86 (SCU). The gear changer control unit 86(FIG. 7) may include a CPU 88 to process signals/commands and the like,a wake sensor 90 operatively connected thereto, a memory component 92, afunction button 94, an indicator such as a LED 96, an output 98 tocontrol/operate the motor unit 84, and a transmitter and receiver 100for sending and receiving wireless signals, which may also be referredto as a gear changer transmitter and receiver. The motor unit 84receives and executes position and/or gear change commands from the gearchanger control unit 86. In the illustrated embodiment, the front gearchanger shifts between two chainrings. Alternatively, more than twochainrings are contemplated. The CPU 88 may also be configured to toggleshift the front gear changer 28 between two chainrings when the functionbutton 94 is pressed then released.

Referring also to FIG. 9, while the rear gear changer 30 and front gearchanger 28 is described as each having a gear changer control unit, asingle shared gear changer control unit 102 could be employed. Theshared gear changer control unit 102 shown is located in a gear changerjunction box 104, but could also be located within the rear gear changer30 or front gear changer 28. The shared gear changer control unit 102may include a power source 184 (battery). The gear changer control unit102 may include a CPU 188 to process signals from the MCU 144, a wakesensor 190, a memory component 192 coupled to the CPU, a function switch194, a LED 196, and a transmitter and receiver 200 configured to sendand receive wireless signals.

In one embodiment, the CPU 88 or 188 may be an Atmel ATmega324PA 8-bitRISC microcontroller with an internal eeprom memory. The transmitter andreceiver 100, 200 may be an Atmel AT86RF231 2.4 GHz transceiverutilizing AES encryption and DSS spread spectrum technology supporting16 frequency channels and the IEEE 802.15.4 communication protocol.

Channel Selection

It is possible to set the system 22 to one of a plurality of differentselectable transmitter and receiver frequency channels to avoidcrosstalk with other systems in the vicinity. A device may be designatedin the system 22 to be the channel master. The channel master device maybe the rear gear changer 30. Prior to pairing devices, (i.e., the shiftunit(s) and gear changer(s)), the rear gear changer 30 would be set to aparticular transmitter and receiver frequency channel. This could beaccomplished by pressing the function button 74 in a certain sequence,or could be accomplished with a selector switch, or could beaccomplished by wireless communication with a device designed to performsuch a task. It is considered that it would be within the skill of theordinary artisan to accomplish such a task.

Pairing

The components of the wireless control system 22 are paired to enablewireless communication therebetween. Referring to FIG. 2 and FIGS. 4-7,each Master Control Unit 44 has a unique “device ID” value and a “devicetype” value permanently stored in the MCU memory component 50. The“device type” value indicates the type of device it is, for example:“right shifter unit” or “left shifter unit”.

For purposes of illustrating an embodiment of a pairing operation, anexample with a front gear changer will be illustrated. It will beunderstood that the basic steps will be the same for a rear gearchanger. The front gear changer 28 containing a gear changer controlunit 86 (SCU) is paired with a shifter 24 containing a MCU 44 asfollows. When a mode changing mechanism, which may be in the form of afunction button 94 on the gear changer, is pressed for a pre-determinedperiod of time, the SCU 86 of the gear changer enters or is converted toa pairing mode. The SCU 86 may slowly flash the LED 96 on the gearchanger 28 to indicate that it is in pairing mode and turn on the SCUtransmitter and receiver 100. At this time, the receiver part oftransmitter and receiver 100 in the SCU 86 scans transmitter andreceiver channels, listening for transmitted signals, wherein listeningmay also be referred to as monitoring. Next, a shift lever/button 38 onthe shift unit 24 with a MCU 44 is pressed and held, causing the MCU totransmit a repeating shift signal that contains the “device ID” and“device type” as part of the signal. When the SCU 86 in the gear changer28 detects the repeating shift signal from a MCU 44, the SCU may changethe LED 96 to solid on. The SCU receiver part of transmitter andreceiver 100 continues to listen for a repeating shift signal from theMCU 44 of the shifter for a pre-determined time period, which may beabout two seconds. Once the SCU 86 of the gear changer 28 has determinedthat it has received a shift signal from the MCU 44 for the requiredperiod of time, the SCU exits the pairing mode and stores the “deviceID” in the SCU memory component 92 in a space reserved for that “devicetype”. If the SCU 86 is the channel master in the system 22, it willalso send a signal to instruct the MCU 44 in the paired shifter 24 tooperate on a particular channel. The shifter 24 and gear changer 28 arenow paired and the gear changer's SCU 86 will respond to commands fromthe MCU 44 of the paired shifter.

The memory 92 of the SCU 86 of the gear changer 28 will only record onedevice ID for each device type. If a shifter 24 with a device id of“234” is paired with a rear gear changer 30, and later another shifter24 with the device ID “154” is paired with the rear gear changer, theSCU 72 memory value “234” in the “device type” space will be overwrittenwith the new value “154,” and the rear gear changer 30 will no longerrespond to the shifter 24 of device ID “234.”

An embodiment of the wireless system 22 has right and left shifters 24a, 24 b; each with a MCU 44, and a front gear changer 28 and a rear gearchanger 30, each with a SCU 86, 66 (FIGS. 6 and 7). Therefore, it willbe understood that the pairing process will be repeated four (4) timesfor this embodiment. The rear gear changer 30 will be paired to each ofthe right and left shifters 24 a, 24 b and the front gear changer 28will be paired to each of the right and left shifters. This creates ahighly secure system because physical access is required to press thebuttons on the components to pair the devices. Further, each gearchanger 28, 30 will respond only to shifters with which they have beenpaired. If the operator verifies that each shifter 24 a, 24 b controlseach of the gear changers 28, 30, they can be confident that nounauthorized shifters have been paired. In an alternative embodiment,where a pair of shifters 124 a, 124 b shares a MCU 144 or the front andrear gear changers 28, 30 shares a SCU, the number of pairing steps willbe reduced.

Wake Sensor

Conserving power on battery powered wireless devices is a designconsideration and one contemplated by embodiments of the invention. Ifelectronic devices are left on continuously, batteries tend to bequickly depleted. Therefore, various strategies may be implemented toconserve battery power. The MCU 44 connected with the shift unit(s) 24may be configured to sleep, i.e. are in a relatively low-power statewhen the bicycle/system is inactive. During this time, the CPU 48 is inthe low power state (sometimes known as standby or sleep mode) and thetransmitter and receiver 54 is turned off. The MCU 44 only wakes(becomes fully powered and operational) and transmits signals when aswitch or button is activated, otherwise it sleeps.

For example, the SCU 66 in the gear changer 30 may receive controlsignals from the MCU 44 or, in some cases, other SCUs. If thetransmitter and receiver 80 is left on continuously, the battery 62would be quickly depleted. The SCU 66 may include a wake unit 70 todetermine and signal when the bicycle is being used. In one embodiment,for example, a SignalQuest SQ-MIN-200 or an Freescale SemiconductorMMA8451Q vibration sensor may be used as a sensor for the wake unit.When operating a bicycle, vibrations are caused by uneven road surfacesand drivetrain motion, which are easily detected by sensors (not shown).Other sensors could be used for the wake unit 70, such as accelerometersor magnetic reed switches configured to detect magnets attached tomoving elements of the bicycle 20. When the bicycle 20 is operated,vibration or movement is detected and the wake unit 70 sends a wakesignal to wake the SCU 66 (FIG. 10). The SCU 66, upon becoming fullypowered and operational from a wake signal from the vibration sensor,becomes awake as long as it receives wake signals from the wake unit 70.If wake signals are not received for a period that exceeds apredetermined sleep timeout value, the SCU 66 will go back to sleep. Theduration of the sleep timeout may be about 30 seconds.

Transmitter and Receiver Timing

Power consumption can be further reduced by frequently turningtransmitter and receivers 80, 100 on and off according to apredetermined or given period or cycle when the SCU 66, 86 is awake.When the SCU 66, 86 receives a signal from the wake sensor 70, 90 itenters an awake mode, becoming fully powered and operational. During theawake mode, the SCU 66, 86 turns the transmitter and receiver 80, 100“on” to monitor for shift signals for a listen time A, which may beknown as a listen mode, and then “off” for a wait time B, which may beknown as a non-listen mode, to conserve energy as shown on timeline SCUon the chart. The total of one cycle of time A and B defines a givenawake mode cycle period or awake mode cycle time. Typically, listen modetime A might be about 5 ms and wait time or non-listen mode B might beabout 45 ms. In this state, the SCU transmitter and receiver 80, 100 ison (in listen mode) only about 10% of the time of the awake mode cycletime.

FIG. 11 shows the transmitter and receiver timing when shift signals aretransmitted from the MCU 44 to the SCU 66, 86. After a shift button 38on the shift unit 24 is pressed, the MCU 44 enters a wake mode or state,waits for the channel to become clear, and transmits a series ofduplicate control/shift signals if no other signals or noise isdetected. Each of the duplicate shift signal has a duration time of C(about 1 ms) followed by a rest period time D (about 2 ms) and isrepeated for a length of time, i.e., a message duration time F (about100 ms). The message duration time F is chosen so that the shift signalfrom the MCU 44 will coincide with at least one time when thetransmitter and receiver 80, 100 of the SCU 66, 86 is activelymonitoring or listening, i.e. in a listen mode. In the example shown inFIG. 11, four control signals coincide with the time the SCU transmitterand receiver 80, 100 is in listen mode, as illustrated by the dashedlines. In other words, the gear changer transmitter and receiveractively listens for the shift signals from the shifter transmitter andreceiver during a part of an awake mode cycle time and the shiftertransmitter and receiver is configured to transmit the shift signals fora length of time which is greater than the awake mode cycle time toensure that the gear changer transmitter and receiver will be in a stateof active listening when a shift signal is being transmitted, whereinlistening may also be referred to as monitoring.

When the SCU transmitter and receiver 80, 100 hears a shift or controlsignal, the SCU 66, 86 keeps the transmitter and receiver in listenmode, even if the detected signals are intended for another device. TheSCU transmitter and receiver 80, 100 will stay in listen mode for alisten duration time G (about 20 ms) after the last signal is receivedbefore going back to sleep, i.e. the non-listen mode, to conserve power.It will be understood that the various timings illustrated herein areexemplary in nature.

During racing or large group rides it is inevitable that cyclists willbe using a number of systems in detectably close proximity. Both the MCU44 and SCU 66, i.e., 86, may have special features to enable coexistenceand ensure high reliability during crowded use. The MCU transmitter andreceiver 54 has the ability to both transmit and receive signals. Priorto transmitting a wireless signal, the MCU 44 will listen to determineif other transceivers or devices are transmitting. These othertransceivers may or may not be part of the instant system. When the MCU44 hears other transceivers, prior to transmitting, it will observe thedevice ID(s) of the other signal(s) and count these devices until itsees a device repeated. When the MCU 44 determines that the channel isclear to transmit after hearing other transmissions, (i.e., anytransmission that is not from a master control unit to which either ofthe SCUs 66, 86 is paired, wherein the other transmissions may bereferred to as noise), it will begin transmitting a signal but mayadjust the repeat interval by increasing the time between transmissionsof the duplicate signals to avoid collisions with the othertransmissions/noise.

FIG. 12 shows the interaction of three MCUs that attempt to transmit atthe same time. The timeline MCU1 shows the sleep (low power mode), wake(fully powered and including an actively monitoring mode), and transmit(TX) states of the first MCU. When a shift actuator is operated, the MCUwakes and pauses to listen for a quiet time (J) before transmittingsignals (S11-S14). Since no other signals or noise in this example wereheard during quiet time J, S11-S14 are repeated at a minimum repeat rateE (about 3 ms). When the MCU is awake, between transmitting signals, itlistens for signals from other transmitters.

MCU2 wakes from a TX command request and begins listening at time T2.After MCU2 receives signal S13 and S14, both from a common MCU, itdetermines that two devices will be transmitting and begins sendingsignals S21-S25 at time T3 and at a repeat rate E2, about 6 ms. MCU2transmits signal S21 at time T3 before S15 of MCU1, thus “bumping” S15.MCU1 was listening between S14 and the planned S15 signal and heard thesignal S21 from MCU2. MCU1 then cancels S15 and begins sending a newsignal S15′-S18 starting at time T4 at repeat rate E2. MCU1 chooses tosend signal S15′ about 3 ms from T3, maintaining an interval betweenduplicate signals at a first interval or environmental signal repeatrate of about 3 ms.

MCU3 wakes prompted by detection of a TX command request (shift signal)and begins listening at time T5. After MCU3 receives signal S24, S18,and S25, where S24 and S25 are both from a common MCU, it determinesthat three devices will be transmitting and begins sending signalsS31-S35 at time T6 and at a repeat rate E3, about 9 ms. Signal S31 wastransmitted prior to the planned signal S19 of MCU1. MCU1 was listeningbetween signals S18 and planned S19 and received S25 from MCU2 and S31from MCU3. MCU1 then cancels S19 and begins sending a new signalS19′-S1B starting at time T7 at repeat rate E3. MCU1 chooses to sendsignal S19′ about 3 ms from T6, maintaining an environmental signalrepeat rate of about 3 ms. Signal S19′ was transmitted prior to theplanned S26 of MCU2, bumping that signal. MCU2 was listening betweensignals S25 and planned S26 and received S31 from MCU3 and S19′ fromMCU1. MCU2 then cancels S26 and begins sending a new signal S26′-S2Astarting at time T8 at repeat rate E3. MCU2 chooses to send signal S26′about 3 ms from T7, maintaining an environmental signal repeat rate ofabout 3 ms.

Between S28 and S29, MCU2 observed that only S34 was received from MCU3and determines that only two devices are now communicating. After S29,MCU2 sends signals S2A-S2B at the increased repeat rate E2. Between S34and S35, MCU3 observed that only S29 was received from MCU2 and alsodetermines that only two devices are now communicating. After S35, MCU3sends signals S35-S38 at the increased repeat rate E2. Between S37 andS38, MCU3 observed that no signals were received and it alone iscommunicating. After S38, MCU3 sends signals S38-S3A at the increasedrepeat rate E.

Although the example above describes the transmitters adjusting theirrepeat intervals on the next transmit cycle, it may be desirable to waitmore than one cycle before adjusting the repeat rate. This gives thetransmitters more chances to notice other transmitters they might nothave noticed on their initial tally.

There is a risk that two devices will attempt to send signals at exactlythe same time. To reduce the possibility of collisions, the signalrepeat rate E may be randomly varied by as much as plus/minus 1 ms, forexample.

Also, the invention may include a method to maximize reliability thereofby maximizing the number of sent duplicate shift signals correspondingto the input signal in a given message duration time. If the repeatinterval of the plurality of duplicate shift signals creates a situationwhere only a small number of duplicate shift signals can be transmitted,the system may increase the length of the message duration time totransmit a sufficient number of the duplicate signals at the increasedinterval rate.

Handling Duplicate Shift Commands

Because the MCU 44 of the shifter 24 sends the shift signal multipletimes, the SCU 66, 86 of the gear changers 30, 28 need a method ofdiscerning duplicate received shift signals from new shift signals. Whenthe MCU 44 generates a shift signal it also generates a “count value”that is transmitted along with the device ID and device type. Each timea new shift signal is generated by the SCU 66, 86 a new count value isgenerated by retrieving the previous count value from memory andincreasing the value by one (1) to obtain a new count value. When theSCU 66, 86 receives a shift signal it compares received count value tothe previously received count value stored in the SCU memory 72, 92 forthat signal type (ex: upshift, downshift) and device type (rightshifter, left shifter). If the count value, signal type, and device typematch the values stored in memory, the command is ignored as it is aduplicate signal that has already been processed. If the count value isdifferent than the value stored in memory, the SCU 66, 86 will calculatea value “pending” by subtracting the count value in memory from thereceived count value. If the operator pushes the upshift lever once andno wireless transmissions were lost, the SCU 66 calculates a value ofpending=1 and executes a command to the motor unit 64 to upshift once.Then the SCU 66 will record the new count value to memory for thatsignal type and device type. However, if the operator is rapidlypressing the upshift lever 38 and the system 22 is in a noisy wirelessenvironment where wireless signals fail often, the SCU 66 may calculatea pending value greater than one. In this case a shift signal was lost,or the operator pressed the lever 38 more than once before the SCU 66turned its transmitter and receiver on. If the SCU 66 receives a shiftsignal corresponding to an upshift input signal and calculates a pendingvalue of 3, it is known that the upshift lever 38 had been operatedthree (3) times since the last shift signal corresponding to an upshiftinput signal was received, and will send a command to the motor unit 64to upshift three (3) times. Then the SCU 66 will record the new countvalue to memory for that signal type and device type. The SCU 66 willalso ignore signals corresponding to upshift or downshift input signalswhen the gear changer 30 is at the limit of its range. For this tooccur, the SCU 66 will keep track of its position.

Other Shift Methods

The MCU 44 can also generate control signals regarding the state of theshift buttons 38 (upshift & downshift). For example, when an upshiftbutton 38 of unit 24 a is pressed, the MCU transmits an “upshift buttonpressed” signal and when the upshift button is released, transmits an“upshift button released” signal. This feature is useful in a system 22where there is no dedicated front gear changer shift button 42 on theshift units and the front gear changer 28 is toggle shifted by pressingthe upshift and downshift buttons 38 of both units 24 a, 24 b together.In the case of a front shift, the SCUs 66, 86 will first receive both anupshift & downshift button-pressed signal before receiving an upshift ordownshift button-released signal, indicating that both buttons werepressed before either is released. When the SCU 86 of front gear changer28 receives this signal sequence it will perform a front gear changertoggle shift. When the rear gear changer 30 receives this signalsequence, it will ignore them.

If the rear gear changer SCU 66 receives an upshift or downshiftbutton-released signal without first receiving an upshift or downshiftbutton-pressed signal, it can infer that the button-closed signal waslost or not transmitted from the MCU 44 because the button 38 wasrapidly pressed and released. In this case the rear gear changer SCU 66will go ahead and perform the upshift or downshift.

Although transmitted signals have only been described from the MCU 44,the SCU 86, 66 in the front gear changer 28, and rear gear changer 30may also send signals to other devices. For example, the rear gearchanger 30 can send a message to the front gear changer 28 indicatingthe current gear position of the rear gear changer. This would allow thefront gear changer 28 to optimize the trim position of the front gearchanger based on the position of the rear gear changer 30. Other typesof data the SCU 66, 86 of a device could transmit include battery level,number of shifts, device ID, temperature, error codes, firmware version,etc.

ANT/BTLE Bridge

It is also possible for the present system 22 to communicate with otherthird party devices using standard protocols such as ANT or BluetoothSmart (BTLE). One of the devices in the system can collect data from theother devices such as battery level, gear position, firmware version,etc. and share the data with a third party device using a differentcommunication protocol, effectively operating as an information bridge.

While this invention has been described by reference to particularembodiments, it should be understood that numerous changes could be madewithin the spirit and scope of the inventive concepts described.Accordingly, it is intended that the invention not be limited to thedisclosed embodiment, but that it have the full scope permitted by thelanguage of the following claims.

The invention claimed is:
 1. A wireless control system for a bicycle,comprising: at least one shift unit including a shift actuator and amaster control unit in communication with the shift actuator; the mastercontrol unit transmitting on a channel and listening for noise on thechannel and after receiving an input signal from the shift actuatortransmitting a plurality of shift signals corresponding to the inputsignal for a message duration time if the channel is free of noise. 2.The wireless control system of claim 1, wherein the master control unitwakes upon receipt of the input signal from the shift actuator.
 3. Thewireless control system of claim 1, wherein the master control unitalters the time between the transmissions of the shift signals so thatthe shift signals do not occur during the noise.
 4. The wireless controlsystem of claim 1, wherein each of the plurality of shift signals isspaced from an adjacent one of the shift signals according to a firstinterval.
 5. The wireless control system of claim 4, wherein the mastercontrol unit listens on the channel for noise between each of theplurality of shift signals.
 6. The wireless control system of claim 5,wherein the master control unit alters the transmissions of the shiftsignals if noise is detected by extending the time between adjacent onesof the plurality of shift signals such that the shift signals are nottransmitted during the noise.
 7. The wireless control system of claim 6,wherein the master control unit transmits the shift signals if noise isdetected according to a second interval, the second interval beinggreater than the first interval.
 8. The wireless control system of claim7, wherein the second interval is about twice that of the firstinterval.
 9. The wireless control system of claim 8, wherein the firstinterval is about 3 milliseconds.
 10. The wireless control system ofclaim 1, further comprising a pair of shift actuators, each of the pairof shift actuators including a master control unit.
 11. The wirelesscontrol system of claim 1, further comprising a pair of shift actuatorsand a master control unit common to both of the pair of shift actuators.12. The wireless control system of claim 1, further comprising at leastone gear changer control unit paired with the master control unit toreceive the plurality of shift signals and act responsively thereto. 13.The wireless control system of claim 10, further comprising a pair ofgear changer control units, each of the pair of gear changer controlunits paired with each of the master control units.
 14. The wirelesscontrol system of claim 3, wherein the time between the transmissions ofshift signals is randomly varied to reduce the chance of collisions.